There is at present a phenomenon of unexplained small holes appearing in outer upper garments of mainly women. These holes generally appear in the area of the navel and are more commonly found in looser fitting tops. A search using a common search engine on the internet brings up thousands of references and reveals numerous chat forums where the effect is discussed.
By way of illustration the following item was published in The Sydney Morning Herald—an Australian newspaper on 15 Jan. 2012:                “For years I have been mystified by tiny holes that have appeared in my T-shirts, polo shirts and thin sweaters—dead centre in the belly-button area and often very soon after buying them.” writes a baffled . . . , of Redfern. “I thought it was my washing machine but now I'm convinced it's my belt or my jeans, though I haven't gone through a scientific process of elimination. I thought I was alone until I Googled it, and it looks like it's a huge problem. If you enter ‘tiny holes in shirts’ you'll find a forum that's been attracting opinions since 2009, with no one really sure what the culprit is—belts, trousers, seatbelts, bugs, stomach discharge, counter tops, tables, fabric dye, you name it. I'd be interested to know how widespread these garment-destroying mystery holes are among Column 8 readers' wardrobes”        
The problem is clearly a world wide problem and damage to clothing will be measured in hundreds of millions of dollars per annum. Numerous and diverse causes and cures are proposed but none that appear to answer for the majority. The cause as outlined below is not documented and nor is any cure. To understand the cause of the problem it is first necessary to understand the phenomena of triboelectric charge and damaging electrostatic discharge.
The science of static electrical charge generation is well understood and documented in the literature. For the purposes of this application the following summary is relevant. Reference is made in particular to “Triboelectric Generation: Getting Charged” by Ryne C. Allen—Evaluation Engineering 2000.
Static electrical charge can be generated when two surfaces in contact separate. By “in contact” we mean in contact at the molecular level where in general the two surfaces are separated by a distance of less than 4 Angstrom Units. This phenomenon is called triboelectric charging or tribocharging and is caused by the stripping of free electrons (valence electrons or electrons in the outermost shell of a molecule) from one surface to the other when the surfaces separate. Tribocharging results in a non-neutral surface charge on both surfaces. One surface attains a positive and the other a negative surface charge with respect to each other. A voltage difference between the 2 surfaces results. Given the right conditions the voltage difference can be considerable and measured in kilovolts.
The level and polarity of the tribocharge is dependent on a number of factors but importantly including:                The “work function” of each of the materials where the work function is a measure of the difficulty (or energy required) to liberate free electrons from a solid to a point outside the material. Or more simplistically the ease with which free electrons can be stripped from the material. A low work function means a greater ability to give up electrons. Accordingly materials with a greater disparity of work functions will in general result in a greater tribocharge.        The surface area of separation (at the molecular level) of contact between the surfaces. Where a greater separation of surface area will in general result in a greater tribocharge.        Charge backflow where some of the charge imbalance resulting from separation flows back from one material to the other. To the extent that charge backflow occurs the tribocharge will be reduced.        Corona discharge where the potential difference between the 2 surfaces (particularly at surface irregularities) is such that the dielectric strength of the gas between the surfaces is exceeded and charge flows back through a path of ionized gas.        
Any resultant tribocharge is also dependent on the presence of moisture both as humidity and as surface moisture whereby charge backflow is increased significantly by the presence of moisture.
A non-exact ranking of the relative ability of various materials to tribocharge is given by the triboelectric series. The triboelectric series lists materials by their propensity to give up or attain electrons when in contact with another material. The list reproduced below has materials with a greater propensity to lose electrons (attain a positive charge) at the top down through neutral to the materials with a greater propensity to gain electrons (attain a negative charge) at the bottom where cotton is about neutral.
TABLE 1Triboelectric SeriesPositive ChargeHuman skin (Dry)Rabbit FurGlassHuman HairNylonWoolSilkAluminiumPaperNo ChargeCottonSteelNo ChargeWoodHard RubberNickel, CopperBrass, SilverGold, PlatinumAcetate Fibre (Rayon)PolyesterCling FilmAcrylicPolyurethanePolythenePolypropylenePVCSiliconTeflonNegative ChargeSilicone Rubber
In general separating materials further apart from each other on the triboelectric series will result in a greater resultant tribocharge. For example polyester in contact with wool, nylon or silk can generate significant tribocharge but even polyester and cotton are far enough away from each other to generate appreciable tribocharge. Unfortunately the worst effects can involve silk and wool—both delicate and expensive fabrics that can be easily damaged.
The surface area of separation is dependent on the gross surface area of contact, the surface roughness of each surface and the contact force. A low surface roughness implies a greater area of molecular contact per unit of gross surface contact and a higher contact force also implies a greater area of molecular contact per unit of gross area.
Rubbing one surface against another is merely a means of greatly increasing the surface area of contact being separated. To the extent that separation of the surfaces is produced by a rubbing action then the coefficient of friction between the two surfaces is important in that it is a relative measure of the surface roughness between the surfaces.
So in general a higher tribocharge can be expected from rubbing materials together that have a greater separation on the triboelectric series and with higher contact force and with smoother surfaces.
Possibly the most common and well known triboelectric effect is that associated with garments. Most people have experienced an electric shock caused by the discharge of tribocharge when touching the metal surface of a vehicle after getting out of it. The tribocharge arising from the separation of the wearer's outer garment from the car upholstery surface and the electric shock resulting from the discharge to ground. Similarly when removing an outer garment of dissimilar material to an inner garment the crackling of a corona discharge and the electrostatic attraction between the garments may be observed.
Potential exists for a significant tribocharge to be generated between a woman's brassiere and an outer garment in contact with it. Whilst henceforth in this specification we refer to a brassiere we also include inner garments such as singlets and camisoles where the effect can also be observed. In general in a system where surface separation is occurring more or less continually any tribocharge will increase until the combined discharge effect equals the charge effect when the system will reach a steady state. At steady state a circuit can exist with electrons transferring from one surface to the other and then back to the original surface through the skin (a good conductor) of the wearer. It follows that the points of contact between the outer garment and the skin of the wearer can become part of the circuit with the electron flow taking the route of least resistance. The tribocharge arising from such intergarment contact will be affected by the following:                The separation of the outer material of the brassiere and the outer garment on the triboelectric series. A greater separation will in general result in a greater charge.        The extent to which the 2 garments rub or slide together. More relative surface movement will result in a greater tribocharge.        The moisture content of the garments and the relative humidity of the surrounding air.        The relative surface roughness or coefficient of friction between the brassiere and outer garment.        The contact force between the garments.        
The tribocharge generated between the fabrics can be in the order of thousands of volts. An experiment carried out to estimate the static electric field generated between dissimilar garments around the breast area as part of the Conundrum Project (cancer6million.org) dealing with the electrophysiology of cancer demonstrated that charges of over 5000 volts could be generated with just 4 distinct rubs between polyester and acrylic fabrics. Whilst not in any way connected to the problem herein discussed the potential for large tribocharges was clearly demonstrated. Continual relative movement or rubbing will generate even larger charges. Where the outer garment is tucked in, in contact with the skin or in very close proximity to it over a large surface area the tribocharge can dissipate harmlessly over a large area back to the body.
U.S. Pat. No. 6,488,564 describes a system for reducing electrostatic fields in the breast area that might cause tissue damage by using electrically conductive electrostatic field concentrators adapted to ionize air molecules in the vicinity and thereby reduce electrostatic fields. This citation describes voltages measured between brassiere and outer garment of thousands of volts.
When the outer garment remains loose and is not forced into skin contact the tribocharge can increase significantly. Furthermore at any distinct points of discharge the tribocharge can concentrate (in the manner of a lightning rod) and corona discharge can occur. Corona discharge not only results in the removal of material from both electrodes in the manner of spark erosion but also generates extremely high temperatures associated with the plasma generated by the discharge. As a consequence the fabric in close proximity to the discharge is damaged by the combined effect of spark erosion and heat. The dielectric strength of air is approximately 3 kvolts/mm. Accordingly a triboelectric potential difference of only 5000 volts could result in a spark jumping nearly 2 mm at a distinct discharge point.
A distinct discharge point can be formed when any conductor is in contact or even in close proximity to the skin. Such a conductor might take the form of a metal stud or similar such as exists at the top of the fly on a pair of jeans. These studs can be pressed against the skin or against underwear and in close proximity to the skin on the one side and be in close proximity to the outer garment on the other side. The conditions necessary for a corona discharge at a conductor are easily attained and a destructive electrostatic discharge (DED) (as defined herein) occurs. Whilst the metal stud on jeans is a common site of DED any conductor between the outer garment and the skin can become a site of DED; for example metal clips on brassiere straps and belt buckles. It should be noted that it is not necessary that the conductor be in absolute contact with the skin but may only need to be in close proximity to it. For example if the outer garment and brassiere material are far apart on the triboelectric series such as with polyester and wool or nylon and other conditions are favourable there may be a corona discharge between outer garment and conductor and then between conductor and skin. Such could occur with a metal belt buckle not in skin contact. However the exposed metal stud on jeans appears to be the most common conductor and frequently it is pressed against the wearer's skin.
Fashion trends, changes in body shape and the more prevalent use of synthetic fabrics have resulted in DEDs becoming a widespread problem. Some specific factors include:                The move away from cotton as a brassiere material and it's replacement by synthetics (especially polyester) which are further toward the ends of the triboelectric series and therefore more prone to result in a larger difference on the triboelectric series of the materials in contact.        The use of slightly padded more comfortable brassieres that provide an insulating layer between the outer brassiere layer and the skin thus reducing charge backflow that would reduce tribocharge.        The widespread practice of leaving outer garments hanging loose rather than being tucked in.        The more prevalent use of smooth surfaced brassieres as opposed to patterned rougher surfaces        More figure fitting outer garments resulting in higher contact forces between the brassiere and the outer garment at the bust area and also at the midriff.        Increased body weight resulting in:                    closer proximity of outer garment to metal studs, metal buckles or other metal objects at the midriff,            closer proximity and better electrical contact between the skin and the metal studs, buckles etc at the midriff.                        
It is an object of the present invention to address or ameliorate some of the above disadvantages and limitations or to at least provide the public with a useful choice.